Conventional retaining walls are used to secure earth embankments against sliding and slumping. Retaining walls are made of various types of concrete, solid masonry, wood ties, bricks and blocks of stone and concrete. The blocks are placed in rows and superimposed on top of each other to form a wall. An example of blocks used in the construction of retaining walls is shown by Forsberg in U.S. Pat. No. 4,914,876. The foregoing patent discloses blocks stacked in a plurality of courses or layers interlocked by means of elongate pins extending up through a block and into a shallow elongate pocket disposed in the under surface of the next course of blocks.
In addition, a tie-back arrangement has been shown whereby a geogrid sheet is retained by the interconnecting pins. Thus the presence of the geogrid sheet buried in the retained soil behind the wall serves to stabilize the wall and soil.
However, use of the pins as the holding means serves to cause the geogrid sheet to block off the otherwise open cells of the wall. These open cells normally are loaded with pea gravel or other drainage material.
The geogrid sheet, when held as above described, can cause the smaller sizes of drainage material to "bridge" openings of the sheet and prevent complete filling of the open cells. This lack of complete filling can allow the retained earth behind the wall to invade the unfilled cells and prevent proper drainage or cause settlement of the retained earth behind the wall.
In addition, use of the interlocking pin arrangement, as shown in the above patent, leaves the degree of backward and upward slope in the face of the wall in the hands and eye of the worker whereby such slope will generally be inconsistent or erratic along the length thereof.
Thus, use of such tieback material attached at the front of the block (as in the above patent) dictates that pea gravel or other drainage material must be filled into the open cells of the block or formed between blocks) before attachment of the tieback material.